Thermal processing is required in the fabrication of silicon and other semiconductor integrated circuits formed in silicon wafers or other substrates such as glass panels for displays. The required temperatures may range from relatively low temperatures of less than 250° C. to greater than 1000°, 1200°, or even 1400° C. and may be used for a variety of processes such as dopant implant annealing, crystallization, oxidation, nitridation, silicidation, and chemical vapor deposition as well as others.
For the very shallow circuit features required for ultra-large scale integrated (ULSI) circuits, such as shallow implanted source and drains, thermal diffusion can degrade device geometry. Therefore, it is desired to reduce the total thermal budget in achieving the required thermal processing. The thermal budget may be considered as the total time at high temperatures necessary to achieve the desired processing temperature. Such shallow circuit features are essentially confined to the wafer surface, and annealing them requires only that the wafer surface be heated to the requisite temperature. The time that the wafer surface needs to stay at the highest temperature can be very short.
Rapid thermal processing (RTP) uses radiant lamps which can be very quickly turned on and off to heat only the wafer and not the rest of the chamber. Pulsed laser annealing using very short (about 20 ns) laser pulses is effective for heating only the surface layer and not the underlying wafer, thus allowing very short ramp up and ramp down rates.
A more recently developed approach in various forms, sometimes called thermal flux laser annealing or dynamic surface annealing (DSA), is described by Jennings et al. in PCT Appln. No. PCT/2003/00196966 based upon U.S. patent application Ser. No. 10/325,497, filed Dec. 18, 2002 and incorporated herein by reference in its entirety. Similar techniques are disclosed in U.S. Pat. No. 6,531,681 to Markle and U.S. Pat. No. 6,747,245 to Talwar.
The Jennings and Markle versions use CW diode lasers to produce very intense beams of light that strike the wafer as a thin long line of radiation. The line is then scanned over the surface of the wafer in a direction perpendicular to the long dimension of the line beam.